Cover crops have a valuable role as a ‘soil corrective’ according to Gary Zimmer of Midwestern Bio-Ag. Zimmer is a pioneer of biological farming, which places great emphasis on the role of microorganisms and balanced nutrients in maintaining plant health and he will be discussing this at REAP.
Zimmer makes the distinction between soil correctives – used to fix the soil and reduce the limiting factors – and crop fertilisers, which are applied each year to feed the crop, he explains: “Cover crops and green manures can also be considered soil correctives and provide a valuable role in improving the health and resilience of the soil.
“The choice of cover crop will vary according to farm preferences but they are invaluable in breaking pest cycles, improving water infiltration, suppressing weeds, reducing run-off and protecting soil life from extremes of hot and cold.”
Test your plant and the soil
Tissue testing at different growth stages on healthy plants, gives a good picture of the nutrients the plant is able to access from the soil. Many of the nutrients identified in a soil analysis are ‘locked-up’ and not in a format that the plant can use. For example nitrogen needs to be in a soluble form.
Zimmer has experimented with different testing regimes and advises that mineral analysis of tissue, such as roots and leaves, should be done when the plant is growing well and not stressed. “This is a way to check if your fertility program is working and plants are accessing the nutrients they need,” he says.
The form in which nutrients are delivered is also important and he considers mined minerals, which contain other trace minerals, better for the soil life.
“Timing is important, applying all your fertiliser before crop emergence is a waste as the crop is not yet ready to use the nutrients; better to incorporate a slow release fertiliser that will maintain nutrient levels for longer and minimise run-off.
He also draws an analogy between soluble fertiliser and sugar: too large a dose can cause health problems but sufficient at the right time is beneficial.
Stay within your budget
He continues: “It is more important to stay within your fertiliser budget and work towards a goal of balanced soil than to fix everything right now.
“This is why I recommend a balanced fertiliser, including trace minerals, and a plan for getting them into the plants that includes other elements of cultivation.